How to iterate a jagged array?

vb.net arrays jagged-arrays
Akira picture Akira · Sep 8, 2008 · Viewed 8.6k times · Source

This has been driving me crazy for a few days. Why doesn't the following work?

    Dim arr(3, 3) As Integer

    For y As Integer = 0 To arr.GetLength(0) - 1
        For x As Integer = 0 To arr.GetLength(y) - 1
            arr(y, x) = y + x
        Next
    Next

Also, what if the array looked like this instead?

{ {1, 2, 3},
  {4, 5, 6, 7, 8, 9, 9, 9},
  {5, 4, 3, 2}
}

Answer

Joel Coehoorn picture Joel Coehoorn · Sep 8, 2008

Because there is no '2' or '3' dimension. Should be .GetLength(1) instead of .GetLength(y)

Also: in VB.Net array declarations work a little differently. The subscript you specify in the declaration is the last index, not the number of items created like with C# or C++. But the array is still 0-indexed like C# or C++, instead of 1-indexed like VB6. That means that if you move to VB.Net from a different language your array instincts are probably wrong, no matter which language it is. In VB.Net, Dim arr(3,3) As Integer actually creates a 4x4 array.

Related questions

Fastest way to add an Item to an Array

What is the fastest way to add a new item to an existing array? Dim arr As Integer() = {1, 2, 3} Dim newItem As Integer = 4 (I already know that when working with dynamic list of items you should rather use a List, ArrayList …

Read More
.NET data structures: ArrayList, List, HashTable, Dictionary, SortedList, SortedDictionary -- Speed, memory, and when to use each?

.NET has a lot of complex data structures. Unfortunately, some of them are quite similar, and I'm not always sure when to use one and when to use another. Most of my C# and Visual Basic books talk about them …

Read More
lists and arrays in VBA

I am extremely new at writing in VB.NET, and I did not even realise that there was a significant difference between VB.NET and VBA. I have been writing my application in Visual Studio, but I realised that I …

Read More